Can't say if I were in your shoes that Park Assist would be a make or break issue, to be honest. For starters, the software hasn't even existed until very recently so anyone buying a car after the ultrasonics were removed knew (or ought to) what they were getting in to.
Secondly, having seen what Tesla Vision Park Assist is like from various reviews (RSymons is particularly damning), I'd never want to actually rely on it anyway. It might as well be a squiggly line simulator in Toybox for all the use it would be in a situation where you actually would like it to be accurate.